Electro-hydraulic systems are used extensively for the positioning of control valves or other servo devices requiring high thrust and rapid, accurate positioning. Such systems must be calibrated periodically to ensure the proper operation thereof and the accurate positioning of the controlled device. Typically, to achieve satisfactory system calibration, the controlled device must be manually positioned to predetermined positions while various control circuit parameters are manually adjusted. Since the control circuitry is usually remotely located relative to the controlled device, several persons and a communication network are required to complete the calibration process. In addition, in some instance the calibration adjustments are interdependent resulting in a time consuming, iterative calibration process. And lastly, the resulting potentiometer settings, etc., resulting from the calibration process are subject to shifting due to vibration, contact creep, potentiometer aging, etc., all of which can result in inaccurate positioning of the controlled device.
Because of the foregoing, it has become desirable to develop an electro-hydraulic positioning system which can be automatically calibrated.